U.S. patent number 10,364,550 [Application Number 15/554,882] was granted by the patent office on 2019-07-30 for hydraulic drive system of work machine.
This patent grant is currently assigned to Hitachi Construction Machinery Co., Ltd.. The grantee listed for this patent is Hitachi Construction Machinery Co., Ltd.. Invention is credited to Hiroaki Amano, Seiji Hijikata, Shinya Imura, Kouji Ishikawa, Hidekazu Moriki, Ryohei Yamashita.
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United States Patent |
10,364,550 |
Amano , et al. |
July 30, 2019 |
Hydraulic drive system of work machine
Abstract
Disclosed is a hydraulic drive system capable of improving the
fuel efficiency of a work machine by reducing the pressure loss and
drag loss of a hydraulic pump. There are provided an electric motor
M; a third pump P3 driven by the electric motor; a third pump
hydraulic line L3 to which the delivered hydraulic fluid from the
third pump is supplied; a third directional control valve V4
provided in the third pump hydraulic line, switch-operated by an
arm operation device 19, and controlling the flow rate of the
hydraulic fluid supplied to the arm cylinder 8 from the third
hydraulic pump; and a controller 18 drive-controlling the electric
motor, wherein the controller drives the third pump by the electric
motor when a swing/arm combined operation is detected by pilot
pressure sensors S6, S7, S10, S11.
Inventors: |
Amano; Hiroaki (Kasumigaura,
JP), Ishikawa; Kouji (Kasumigaura, JP),
Imura; Shinya (Toride, JP), Moriki; Hidekazu
(Mito, JP), Yamashita; Ryohei (Tsuchiura,
JP), Hijikata; Seiji (Tsukuba, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Hitachi Construction Machinery Co., Ltd. |
Taito-ku, Tokyo |
N/A |
JP |
|
|
Assignee: |
Hitachi Construction Machinery Co.,
Ltd. (Tokyo, JP)
|
Family
ID: |
57441104 |
Appl.
No.: |
15/554,882 |
Filed: |
February 22, 2016 |
PCT
Filed: |
February 22, 2016 |
PCT No.: |
PCT/JP2016/055123 |
371(c)(1),(2),(4) Date: |
August 31, 2017 |
PCT
Pub. No.: |
WO2016/194409 |
PCT
Pub. Date: |
December 08, 2016 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20180038079 A1 |
Feb 8, 2018 |
|
Foreign Application Priority Data
|
|
|
|
|
Jun 2, 2015 [JP] |
|
|
2015-112556 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E02F
9/2004 (20130101); E02F 9/2292 (20130101); E02F
9/2091 (20130101); E02F 9/2271 (20130101); E02F
9/26 (20130101); E02F 9/2296 (20130101); E02F
3/425 (20130101); E02F 9/2285 (20130101); F15B
11/165 (20130101); E02F 9/2075 (20130101); E02F
9/2239 (20130101); E02F 9/2267 (20130101); F15B
11/17 (20130101); E02F 9/2228 (20130101); F15B
2211/7135 (20130101); F15B 2211/6309 (20130101); F15B
2211/88 (20130101); E02F 3/32 (20130101); F15B
2211/31535 (20130101); F15B 2211/31547 (20130101); F15B
2211/20515 (20130101); F15B 2211/71 (20130101); F15B
2211/275 (20130101); F15B 2211/20546 (20130101); F15B
2211/20576 (20130101); F15B 2211/31529 (20130101); F15B
2211/7142 (20130101); F15B 2211/605 (20130101); E02F
9/268 (20130101); F15B 2211/20523 (20130101); F15B
2211/351 (20130101); F15B 2211/6316 (20130101); F15B
2211/45 (20130101); F15B 2211/6313 (20130101); F15B
2211/6651 (20130101) |
Current International
Class: |
E02F
9/22 (20060101); F15B 11/16 (20060101); E02F
9/20 (20060101); E02F 9/26 (20060101); F15B
11/17 (20060101); E02F 3/42 (20060101); E02F
3/32 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2 518 218 |
|
Oct 2012 |
|
EP |
|
3-3897 |
|
Jan 1991 |
|
JP |
|
8-105078 |
|
Apr 1996 |
|
JP |
|
2007-327526 |
|
Dec 2007 |
|
JP |
|
2008-45575 |
|
Feb 2008 |
|
JP |
|
4509877 |
|
Jul 2010 |
|
JP |
|
2013-28962 |
|
Feb 2013 |
|
JP |
|
2014-1793 |
|
Jan 2014 |
|
JP |
|
Other References
International Preliminary Report on Patentability (PCT/IB/338 &
PCT/IB/373) issued in PCT Application No. PCT/JP2016/055123 dated
Dec. 14, 2017, including English translation of Document C2
(Japanese-language Written Opinion (PCT/ISA/237)) previously filed
on Aug. 31, 2017 (10 pages). cited by applicant .
International Search Report (PCT/ISA/210) issued in PCT Application
No. PCT/JP2016/055123 dated May 24, 2016 with English translation
(6 pages). cited by applicant .
Japanese-language Written Opinion (PCT/ISA/237) issued in PCT
Application No. PCT/JP2016/055123 dated May 24, 2016 (5 pages).
cited by applicant .
Extended European Search Report issued in counterpart European
Application No. 16802848.8 dated Jan. 18, 2019 (ten pages). cited
by applicant.
|
Primary Examiner: Leslie; Michael
Assistant Examiner: Quandt; Michael
Attorney, Agent or Firm: Crowell & Moring LLP
Claims
The invention claimed is:
1. A hydraulic drive system of a work machine comprising: an
engine; first and second hydraulic pumps driven by the engine;
first and second pump hydraulic lines to which a delivered
hydraulic fluid from the respective first and second hydraulic
pumps is supplied; at least one first actuator driven by the
hydraulic fluid supplied from the first pump hydraulic line; a
plurality of second actuators driven by the hydraulic fluid
supplied from the second pump hydraulic line; a first directional
control valve provided in the first pump hydraulic line and
controlling a flow rate of the hydraulic fluid supplied to the
first actuator; a plurality of second directional control valves
provided in the second pump hydraulic line and each controlling the
flow rate of the hydraulic fluid supplied to the plurality of
second actuators; a plurality of operation devices operating the
first actuator and the plurality of second actuators by
respectively switch-operating the first directional control valve
and the plurality of second directional control valves; an electric
motor; a third hydraulic pump driven by the electric motor; a third
pump hydraulic line to which a delivered hydraulic fluid from the
third hydraulic pump is supplied; a third directional control valve
provided in the third pump hydraulic line, switch-operated by a
specific operation device of the plurality of operation devices
that operates a specific actuator of the plurality of second
actuators, and controlling the flow rate of the hydraulic fluid
supplied to the specific actuator from the third hydraulic pump; a
plurality of operation amount detection sensors detecting operation
amounts of the plurality of operation devices; and a control device
that is configured to control the electric motor in accordance with
operation amounts of the plurality of operation devices
corresponding to the plurality of second actuators out of the
operation amounts detected by the plurality of operation amount
detection sensors, wherein the control device is further configured
to control the third directional control valve such that the third
hydraulic pump supplies the hydraulic fluid to the specific
actuator, with a hydraulic line that supplies the hydraulic fluid
from the second hydraulic pump to the specific actuator being
restricted, when a combined operation of two or more second
actuators including the specific actuator out of the plurality of
second actuators is detected by the plurality of operation amount
detection sensors.
2. The hydraulic drive system of a work machine according to claim
1, further comprising a load pressure detection sensor detecting a
load pressure in the specific actuator, wherein the control device
does not drive the third hydraulic pump by the electric motor when
a combined operation of two or more second actuators including the
specific actuator out of the plurality of second actuators is
detected by the plurality of operation amount detection sensors,
and the load pressure of the specific actuator detected by the load
pressure detection sensor is higher than a predetermined load
pressure.
3. The hydraulic drive system of a work machine according to claim
1, wherein the specific actuator is an arm cylinder.
4. The hydraulic drive system of a work machine according to claim
1, further comprising an abnormality detection device detecting
abnormality in an electric system including the electric motor,
wherein the control device does not drive the third hydraulic pump
by the electric motor when abnormality in the electric system is
detected by the abnormality detection device.
5. The hydraulic drive system of a work machine according to claim
1, further comprising: a battery accumulating electric power for
driving the electric motor, and a charging rate detection device
detecting a charging rate of the battery, wherein the control
device does not drive the third hydraulic pump by the electric
motor when the battery charging rate detected by the charging rate
detection device is lower than a predetermined charging rate.
Description
TECHNICAL FIELD
The present invention relates to a hydraulic drive system mounted
in a work machine such as a hydraulic excavator or a crane.
BACKGROUND ART
Generally in a hydraulic work machine such as a hydraulic
excavator, a hydraulic pump is rotationally driven by an engine,
and a hydraulic actuator such as a hydraulic cylinder is operated
by a hydraulic fluid delivered from the hydraulic pump. Examples of
such a hydraulic drive system mounted in a work machine are
disclosed in Patent Documents 1 and 2.
In the hydraulic drive system disclosed in Patent Document 1, the
hydraulic fluid delivered from one hydraulic pump is divided and
supplied to a plurality of actuators, thereby allowing a combined
operation.
On the other hand, the hydraulic drive system disclosed in Patent
Document 2 is equipped with two engine-driven hydraulic pumps and
one electric hydraulic pump, and the actuators are driven by
different hydraulic pumps, whereby operational independence in a
combined operation is realized.
PRIOR ART DOCUMENTS
Patent Documents
Patent Document 1: JP-1996-105078-A
Patent Document 2: Japanese Patent No. 4509877
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
In the hydraulic drive system disclosed in Patent Document 1, a
plurality of actuators are driven by a single hydraulic pump, so
that the drag loss generated at the time of rotational drive of the
hydraulic pump is small. However, at the time of the combined
operation, in which a plurality of actuators are driven, pressure
loss is generated at a control restrictor dividing the delivered
hydraulic fluid from the hydraulic pump.
On the other hand, in the hydraulic drive system disclosed in
Patent Document 2, the actuators are driven by different hydraulic
pumps, so that no pressure loss accompanying the flow division is
generated at the time of the combined operation. However, at the
time of a single operation, in which only a bucket configured to be
driven by an electric hydraulic pump is operated, three hydraulic
pumps including engine-driven hydraulic pumps are driven, resulting
in a large drag loss.
The present invention has been made in view of the above problem.
It is an object of the present invention to provide a hydraulic
drive system capable of improving the fuel efficiency of a work
machine by reducing the pressure loss and drag loss of a hydraulic
pump.
Means for Solving the Problem
(1) To solve the above problem, there are provided, in accordance
with the present invention, an engine; first and second hydraulic
pumps driven by the engine; first and second pump hydraulic lines
to which a delivered hydraulic fluid from the respective first and
second hydraulic pumps is supplied; at least one first actuator
driven by the hydraulic fluid supplied from the first pump
hydraulic line; a plurality of second actuators driven by the
hydraulic fluid supplied from the second pump hydraulic line; a
first directional control valve provided in the first pump
hydraulic line and controlling a flow rate of the hydraulic fluid
supplied to the first actuator; a plurality of second directional
control valves provided in the second pump hydraulic line and each
controlling the flow rate of the hydraulic fluid supplied to each
of the plurality of second actuators; a plurality of operation
devices operating the first actuator and the plurality of second
actuators by respectively switch-operating the first directional
control valve and the plurality of second directional control
valves; an electric motor; a third hydraulic pump driven by the
electric motor; a third pump hydraulic line to which a delivered
hydraulic fluid from the third hydraulic pump is supplied; a third
directional control valve provided in the third pump hydraulic
line, switch-operated by a specific operation device of the
plurality of operation devices that operates a specific actuator of
the plurality of second actuators, and controlling the flow rate of
the hydraulic fluid supplied to the specific actuator from the
third hydraulic pump; and a control device drive-controlling the
electric motor in accordance with an operation of the plurality of
second actuators.
In the present invention configured as described above, a specific
actuator can be selectively driven by the second hydraulic pump
driven by the engine and the third hydraulic pump driven by the
electric motor, so that the pressure loss of the second hydraulic
pump and the drag loss of the third hydraulic pump are suppressed,
making it possible to improve the fuel efficiency of the work
machine.
(2) In the above configuration (1), there are preferably further
provided a plurality of operation amount detection devices
detecting operation amounts of the plurality of operation devices,
and the control device drives the third hydraulic pump by the
electric motor when a combined operation of two or more second
actuators including the specific actuator of the plurality of
second actuators is detected by the plurality of operation amount
detection devices.
In this way, at the time of a combined operation of two or more
second actuators including a specific actuator, the specific
actuator is driven by the third hydraulic pump, and no hydraulic
fluid is supplied to the specific actuator from the second
hydraulic pump, so that the pressure loss of the second hydraulic
pump is suppressed.
(3) In the above configuration (2), there is preferably further
provided a load pressure detection device detecting a load pressure
in the specific actuator, and the control device does not drive the
third hydraulic pump by the electric motor when a combined
operation of two or more second actuators including the specific
actuator of the plurality of second actuators is detected by the
plurality of operation amount detection devices, and when the load
pressure of the specific actuator detected by the load pressure
detection device is higher than a predetermined load pressure.
In this way, during a combined operation and heavy load work of two
or more second actuators including a specific actuator, the
specific actuator is driven by the engine-driven second hydraulic
pump, whereby it is possible to suppress the electric power loss of
the electric motor, and to maintain the same operability as that in
the prior art.
(4) In the above configuration (1), the specific actuator is
preferably an arm cylinder.
In this way, the arm cylinder which frequently undergoes a combined
operation during light load work and which requires a great flow
rate is used as a specific actuator that can be selectively driven
by the engine-driven second hydraulic pump and the
electric-motor-driven third hydraulic pump, whereby it is possible
to enhance the effect of reducing the pressure loss of the second
hydraulic pump and the drag loss of the third hydraulic pump.
(5) In the above configuration (1), there is preferably further
provided an abnormality detection device detecting abnormality in
an electric system including the electric motor, and the control
device does not drive the third hydraulic pump by the electric
motor when abnormality in the electric system is detected by the
abnormality detection device.
In this way, when abnormality occurs in the electric system
including the electric motor, the specific actuator is driven by
the engine-driven second hydraulic pump, whereby it is possible to
prevent serious failure related to the electric system, and to
maintain the same operability as that in the prior art.
(6) In the above configuration (1), there are preferably further
provided a battery accumulating electric power for driving the
electric motor, and a charging rate detection device detecting a
charging rate of the battery, wherein the control device does not
drive the third hydraulic pump by the electric motor when the
battery charging rate detected by the charging rate detection
device is lower than a predetermined charging rate.
In this way, when there is a shortage of battery residual amount, a
specific actuator is driven by the engine-driven second hydraulic
pump, whereby it is possible to maintain the same operability as in
the prior art.
Advantage of the Invention
In accordance with the present invention, the pressure loss or drag
loss of a hydraulic pump is reduced, thereby making it possible to
improve the fuel efficiency of a work machine.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of a hydraulic excavator equipped with a
hydraulic drive system according to an embodiment of the present
invention.
FIG. 2 is a schematic diagram illustrating a hydraulic drive system
according to an embodiment of the present invention.
FIG. 3 is a flowchart illustrating the control by a main controller
according to an embodiment of the present invention.
FIG. 4A is a chart illustrating the relationship between an engine
speed and a reference power of first and second pumps in an
embodiment of the present invention.
FIG. 4B is a chart illustrating the relationship between a battery
SOC and a reference power of a third pump in an embodiment of the
present invention.
FIG. 5 is a computation flowchart of a pump reference flow rate
according to an embodiment of the present invention.
FIG. 6 is a chart illustrating the relationship between an arm load
pressure and a third pump reference flow rate correction gain in an
embodiment of the present invention.
FIG. 7 is a block diagram illustrating a data flow from an electric
system to the main controller in an embodiment of the present
invention.
FIG. 8 is a flowchart illustrating an electric system abnormality
flag setting processing by the main controller according to an
embodiment of the present invention.
FIG. 9 is a diagram illustrating the relationship between an arm
cylinder drive mode and energy loss.
MODES FOR CARRYING OUT THE INVENTION
In the following, as an embodiment of the present invention, a case
will be described in which the present invention is applied to a
hydraulic drive system of a hydraulic excavator.
--Configuration--
FIG. 1 is a diagram showing an outward appearance of a hydraulic
excavator according to the present embodiment. The hydraulic
excavator is equipped with a lower track structure 1, an upper
swing structure 2, and a front work device 3.
The lower track structure 1 is equipped with left and right
crawlers 11a and 11b (of which only the left-side one is shown) and
left and right traveling hydraulic motors 12a and 12b (of which
only the left-side one is shown), and travels by driving the left
and right crawlers 11a and 11b by the left and right traveling
hydraulic motors 12a and 12b.
The upper swing structure 2 has a swing frame 2a as a support
mechanism, and mounted on the swing frame 2a are an engine 13 as a
prime mover, an electric motor M (not shown), a generator motor GM
(not shown) connected to the engine 13, hydraulic pumps P1 and P2
driven by the engine 13, a hydraulic pump P3 (not shown) driven by
the electric motor, a swing hydraulic motor 10 swing-driving the
upper swing structure 2 (swing frame 2a) with respect to the lower
track structure 1, a control valve 15 distributing and supplying
the delivered hydraulic fluids from the hydraulic pumps P1 through
P3 to actuators 7 through 10, 12a, and 12b, etc.
The front work device 3 has a boom 4 mounted to the upper swing
structure 2 so as to be vertically rotatable, an arm 5 rotatably
mounted to the distal end of the boom 4, and a bucket 6 rotatably
mounted to the distal end of the arm 5. The boom 4 rotates in the
vertical direction through expansion and contraction of a boom
cylinder 7, the arm 5 rotates in the vertical/front-rear direction
through expansion and contraction of an arm cylinder 8, and the
bucket 6 rotates in the vertical/front-rear direction through
expansion and contraction of a bucket cylinder 9.
FIG. 2 is a schematic diagram illustrating a hydraulic drive system
according to an embodiment of the present invention. The hydraulic
drive system is equipped with the engine 13, the generator motor
GM, the electric motor M, the three hydraulic pumps (hereinafter
referred to as the first through third pumps as appropriate) P1
through P3, the control valve 15, a plurality of actuators 8
through 10, a plurality of operation devices 19 through 21
respectively operating the actuators 8 through 10, and a main
controller as a control device (hereinafter referred to as the
controller as appropriate) 18.
While the boom cylinder 7 of FIG. 1 and the left and right
traveling hydraulic motors 12a and 12b are driven by one of the
first and second pumps P1 and P2, the operation of the actuators 7,
12a, and 12b does not affect the following discussion, so that, in
FIG. 2, the portions related to the driving of the actuators 7,
12a, and 12b is omitted.
The generator motor GM is connected to the output shaft of the
engine 13, and the first and second pumps P1 and P2 are connected
to the output shaft of the generator motor GM. The generator motor
GM is operated by one of or both the drive force of the engine 13
and electrical energy accumulated in a battery 14, and drives the
first and second pumps P1 and P2. The generator motor GM is
connected to the battery 14 and a second inverter INV2 via a first
inverter INV1, and has the function of a generator converting the
power of the engine 13 to electrical energy and outputting it to
the battery 14 or the second inverter INV2, and the function of an
electric motor assist-driving the first and second pumps P1 and P2
by the electrical energy of the battery 14 supplied via the first
inverter INV1.
The third pump P3 is connected to the output shaft of the electric
motor M. The electric motor M is connected to the battery 14 and
the first inverter INV1 via the second inverter INV2, and is
operated by one of or both the electrical energy accumulated in the
battery 14 and the electrical energy generated by the generator
motor GM, driving the third pump P3.
The first and second pumps P1 and P2 are variable displacement
hydraulic pumps, and are controlled in delivery flow rate through
the adjustment of the pump capacities (displacement volumes) via
first and second pump regulators R1 and R2, respectively. The third
pump P3 is a fixed displacement hydraulic pump, and is controlled
in delivery flow rate through the adjustment of the motor speed of
the electric motor M via the second inverter INV2.
The control valve 15 is arranged between the first through third
pumps P1 through P3 and the plurality of actuators 8 through 10,
and distributes and supplies the delivered hydraulic fluids from
the first through third pumps P1 through P3 to the actuators 8
through 10. Inside the control valve 15, there are formed a
plurality of pump hydraulic lines (hereinafter referred to as the
first through third pump hydraulic lines as appropriate) L1 through
L3. In the first pump hydraulic line L1, there is arranged a
directional control valve V2 controlling the direction and flow
rate of the hydraulic fluid supplied to the bucket cylinder 9. In
the second pump hydraulic line L2, there are arranged a directional
control valve V1 controlling the direction and flow rate of the
hydraulic fluid supplied to the arm cylinder 8 and a directional
control valve V3 controlling the direction and flow rate of the
hydraulic fluid supplied to a swing hydraulic motor 10. In the
third pump hydraulic line L3, there is arranged a directional
control valve V4 controlling the direction and flow rate of the
hydraulic fluid supplied to the arm cylinder 8. The delivered
hydraulic fluids from the first through third hydraulic pumps P1
through P3 are guided to the first through third pump hydraulic
lines L1 through L3, respectively, and are supplied to the
actuators 8 through 10 via the directional control valves V1
through V4.
Pump pressure sensors S1 through S3 detecting the delivery
pressures of the first through third pumps P1 through P3 are
respectively mounted to the first through third pump hydraulic
lines L1 through L3, and load pressure sensors S4 and S5 detecting
the load pressure in the arm cylinder 8 are respectively mounted to
a head side hydraulic line L5 and a rod side hydraulic line L6
connecting the arm cylinder 8 and the directional control valves V1
and V4. The detection signals of the pump pressure sensors S1
through S3 and of the load pressure sensors S4 and S5 are inputted
to the controller 18.
The operation device (hereinafter referred to as the arm operation
device as appropriate) 19 is equipped with a pilot valve 19a, and
an operation lever 19b (hereinafter referred to as the arm
operation lever as appropriate) connected to the pilot valve 19a.
The pilot valve 19a is connected to a pilot hydraulic fluid source
17 formed by a pilot pump, a pilot relief valve, etc., and reduces
a pilot primary pressure inputted from the pilot hydraulic fluid
source 17 in accordance with the operational direction and
operation amount of the operation lever 19b, outputting it as pilot
pressures PL1 and PL2. The pilot pressures PL1 and PL2 are
respectively guided to left pilot pressure receiving portions of
the directional control valves V1 and V4 for the arm operation and
to right pilot pressure receiving portions of the directional
control valves V1 and V4 to switch-operate the directional control
valves V1 and V4 to one of the right and left sides. Pilot pressure
sensors S6 and S7 detecting the pilot pressures PL1 and PL2 are
each mounted to the two pilot hydraulic lines connected to the
pilot valve 19a, and the detection signals of the pilot pressure
sensors S6 and S7 are inputted to the controller 18.
The operation device 20 (hereinafter referred to as the bucket
operation device as appropriate) is equipped with a pilot valve
20a, and an operation lever (hereinafter referred to as the bucket
operation lever as appropriate) 20b connected to the pilot valve
20a. The pilot valve 20a is connected to the pilot hydraulic fluid
source 17, and reduces the pilot primary pressure inputted from the
pilot hydraulic fluid source 17 in accordance with the operational
direction and operation amount of the operation lever 20b,
outputting it as pilot pressures PL3 and PL4. The pilot pressures
PL3 and PL4 are respectively guided to a left pressure receiving
portion and to a right pilot pressure receiving portion of the
directional control valve V2 for the bucket operation to
switch-operate the directional control valve V2 to one of the right
and left sides. Pilot pressure sensors S8 and S9 detecting the
pilot pressures PL3 and PL4 are each mounted to the two pilot
hydraulic lines connected to the pilot valve 20a, and the detection
signals of the pilot pressure sensors S8 and S9 are inputted to the
controller 18.
The operation device 21 (hereinafter referred to as the swing
operation device as appropriate) is equipped with a pilot valve
21a, and an operation lever connected to the pilot valve 21a
(hereinafter referred to as the swing operation lever as
appropriate) 21b. The pilot valve 21a is connected to the pilot
hydraulic fluid source 17, and reduces the pilot primary pressure
inputted from the pilot hydraulic fluid source 17 in accordance
with the operational direction and operation amount of the
operation lever 21b, outputting it as pilot pressures PL5 and PL6.
The pilot pressures PL5 and PL6 are respectively guided to a left
pilot pressure receiving portion and to a right pilot pressure
receiving portion of the directional control valve V3 for the swing
operation to switch-operate the directional control valve V3 to one
of the right and left sides. Pilot pressure sensors S10 and S11
detecting the pilot pressures PL5 and PL6 are each mounted to the
two pilot hydraulic lines connected to the pilot valve 21a, and the
detection signals of the pilot pressure sensors S10 and S11 are
inputted to the controller 18.
The controller 18 monitors the detection values of the pump
pressure sensors S1 through S3 (the delivery pressures of the first
through third pumps P1 through P3) such that the first through
third pumps P1 through P3 do not exceed a limited value, and sets
the target flow rates of the first through third pumps P1 through
P3 in accordance with the detection values of the pump pressure
sensors S1 to S3 (the delivery pressures of the first through third
pumps P1 through P3), the detection values of the load pressure
sensors S4 and S5 (the arm load pressure) and the detection values
of the pilot pressure sensors S6 through S11 (the pilot pressures
P1 through P6), controlling the capacities (displacement volumes)
of the first and second pumps P1 and P2 and the motor speed of the
electric motor M such that the delivery flow rates of the first
through third pumps P1 through P3 coincide with the respective
target flow rates. The pump capacities (displacement volumes) of
the first and second pumps P1 and P2 are controlled through the
transmission of tilting control signals to the first and second
pump regulators R1 and R2 by the controller 18, and the motor speed
of the electric motor M is controlled through the transmission of
an motor speed control signal to the second inverter INV2 by the
controller 18.
--Control--
A method of controlling the hydraulic drive system according to the
present embodiment will be described with reference to FIG. 3.
FIG. 3 is a flowchart illustrating the control by the controller
18. The steps constituting the control flow of FIG. 3 will be
sequentially described below.
In step S101, referring to a pre-set table (an example of which is
shown in FIG. 4A), a first/second pump reference power Pow12 is
determined from the current engine speed or the engine speed target
value. It is noted here that the table is set such that the
first/second pump reference power Pow12 does not exceed the maximum
engine output power HP1.
In step S102, referring to a pre-set table (an example of which is
shown in FIG. 4B), a third pump reference power Pow3 is determined
from the battery charging amount (SOC). It is noted here that the
table is set such that the third pump reference power Pow3 does not
exceed the maximum output power HP2 of the electric motor M and
that when the battery residual amount becomes less than a
predetermined battery residual amount (SOC2), the third pump
reference power is reduced to zero.
In step S103, it is determined whether or not an electric system
abnormality flag is OFF. When the electric system abnormality flag
is OFF, the controller 18 advances to step S105. When the electric
system abnormality flag is ON, the controller 18 advances to step
S104, in which the third pump reference power Pow3 is set to zero,
and then advances to step S105.
In step S105, based on the computation flow shown in FIG. 5, the
reference flow rates Q1c, Q2c, and Q3c of each pump are determined
from various operation signals, first through third pump delivery
pressures (the detection values of the pump pressure sensors S1
through S3) Sv1 through Sv3, and the pump reference powers Pow12
and Pow3.
In the computation flow of FIG. 5, a flow for computing the
reference flow rates of the first and second pumps P1 and P2 will
be first described.
First, referring to a table T1, and the flow rate Q1a is determined
from the maximum operation pilot pressure value PLm1 of the
actuators connected to the first pump P1. Similarly, referring to a
table T2, and the flow rate Q2a is determined from the maximum
operation pilot pressure value PLm2 of the actuators connected to
the second pump P2.
Next, a flow rate Q12b is calculated in accordance with the
following equations from the first and second pump delivery
pressures Sv1 and Sv2 and the first/second pump reference power
Pow12 (flow rate computation C1). P12=(Sv1+Sv2)/2
Q12b=Pow12b/P12.times.60
Finally, the minimum value of Q1a and Q12b is set as the first pump
reference flow rate Q1c, and the minimum value of Q2a and Q12b is
set as the second pump reference flow rate Q2c.
Next, with reference to the computation flow of FIG. 5, the
computation flow for the reference flow rate of the third pump P3
will be described.
First, referring to a table T3, the flow rate Q3a is determined
from the maximum value PLm3 of the operation pilot pressure of the
actuators connected to the third pump P3.
Next, the flow rate Q3b is calculated in accordance with the
following equation from the third pump delivery pressure Sv3 and
the third pump reference power Pow3 (flow rate computation C2).
Q3b=Pow3b/Sv2.times.60
Finally, the minimum value of Q3a and Q3b is set as the third pump
reference flow rate Q3c. It is noted here that particularly when
the third pump reference power Pow3 is reduced to zero in steps
S102 and S104, the third pump reference flow rate Q3c is reduced to
zero.
In step S106, it is determined from the operation pilot pressure
sensor values whether or not the arm operation and the swing
operation are being simultaneously performed. When they are being
performed simultaneously, the controller 18 advances to step S108.
When they are not being performed simultaneously, the controller 18
advances to step S107, in which the third pump reference flow rate
Q3c is set to zero.
In step S108, referring to a pre-set table (an example of which is
shown in FIG. 6), a correction gain G is determined from the
detection values Sv4 and Sv5 of the load pressure sensors S4 and
S5, and the third pump reference flow rate is corrected by the
following equation. Q3c'=Q3c.times.G It is noted here that the
value of G ranges from 0 to 1 and takes a value of 0 when the
actuator load pressure is of a certain fixed value (Pam2 in FIG. 6)
or more.
In step S109, the corrected third pump reference flow rate Q3c' is
subtracted from the second pump reference flow rate, and the
corrected second pump reference flow rate Q2c' is computed.
Q2c'=Q2c-Q3c'
In step S110, the first through third pump target flow rates Q1d,
Q2d, and Q3d are determined. It is noted here that the first pump
target flow rate Q1d is set to Q1c, the second pump target flow
rate Q2d is set to the corrected second pump reference flow rate
Q2c', and the third pump target flow rate Q3d is set to the
corrected third pump reference flow rate Q3c'.
In step S111, the first and second pump target displacement volumes
are computed from the first and second pump target flow rates Q1d
and Q2d and the current engine speed or the target engine speed,
and tilting commands are transmitted to the first and second pump
regulators R1 and R2.
In step S112, the electric motor target motor speed is computed
from the third pump target flow rate Q3d and the third pump
displacement volume, and an electric motor speed command is
transmitted to the second inverter INV2 to control the electric
motor speed, and the flow is completed.
Next, a battery charging rate obtaining method and an electric
system abnormality flag setting method by the main controller 18
will be described with reference to FIGS. 7 and 8.
FIG. 7 is a block diagram illustrating a data flow from an electric
system 30 to the main controller 18. The electric system 30 is
configured with devices related to the driving of the third pump
P3, such as the battery 14, the generator motor GM, the electric
motor M, the first inverter INV1, and the second inverter INV2. A
battery controller 22 mounted on the battery 14 calculates the
battery charging rate based on the battery temperature, the battery
voltage, and the battery electric current value, and transmits it
to the main controller 18. Further, the battery controller 22 sets
a battery abnormality flag to OFF or ON based on the battery
temperature, and transmits it to the main controller 18. It is
noted here that when the battery temperature is within its normal
temperature range, the battery abnormality flag is set to OFF, and
when the battery temperature deviates from its normal temperature
range, it is set to ON.
The first inverter controller 23 mounted in the first inverter INV1
sets a generator motor abnormality flag to OFF or ON based on the
inverter temperature and the generator motor temperature received
from a generator motor thermistor 25 mounted to the generator motor
GM, and transmits it to the main controller 18. It is noted here
that when the inverter temperature and the generator motor
temperature are each within its normal temperature range, the
generator motor abnormality flag is set to OFF, and when the
inverter temperature or the generator motor temperature deviates
from its normal temperature range, it is set to ON.
The second inverter controller 24 mounted in the second inverter
INV2 sets an electric motor abnormality flag to OFF or ON based on
the inverter temperature and the electric motor temperature
received from an electric motor thermistor 26 mounted to the
electric motor M, and transmits it to the main controller 18. It is
noted here that when the inverter temperature and the electric
motor temperature are each within its normal temperature range, the
electric motor abnormality flag is set to OFF, and when the
inverter temperature or the electric motor temperature deviates
from its normal temperature range, it is set to ON.
FIG. 8 is a flowchart illustrating electric system abnormality flag
setting processing by the main controller 18. The steps
constituting the flow of FIG. 8 will be sequentially described
below.
First, the main controller 18 determines whether or not the battery
abnormality flag received from the battery controller 22 is OFF
(step S201).
When the determination in step S201 is YES (the battery abnormality
flag is OFF), it is determined whether or not the generator motor
abnormality flag received from the first inverter controller 23 is
OFF (step S202).
When the determination in step S202 is YES (the battery abnormality
flag is OFF), it is determined whether or not the electric motor
abnormality flag received from the second inverter controller 24 is
OFF (step S203).
When the determination in step S203 is YES (the electric motor
abnormality flag is OFF), the electric motor abnormality flag is
set to OFF (step S204), and the flow is completed.
On the other hand, when the determination in one of steps S201
through S203 is NO, the electric system abnormality flag is set to
ON (step S205), and the flow is completed.
Through the above flow, when all the apparatuses constituting the
electric system 30 are normal, the electric system abnormality flag
is set to OFF, and when abnormality occurs in one of the
apparatuses constituting the electric system 30, the electric
system abnormality flag is set to ON.
--Operation--
The operation of the hydraulic drive system realized by the
above-described control flow of the controller 18 will be described
with reference to FIG. 2.
(Arm/Bucket Combined Operation)
When the arm operation lever 19b and the bucket operation lever 20b
are simultaneously operated, the pilot pressures PL1 and PL2 and
the pilot pressures PL3 and PL4 are respectively outputted from the
pilot valves 19a and 20a in accordance with the operational
direction and operation amount of each lever.
The controller 18 sets the target flow rates of the first and
second pumps P1 and P2 in accordance with the delivery pressures of
the first and second pumps P1 and P2 (the detection values of the
pump pressure sensors S1 and S2), and controls the tilting angles
of the first and second pumps P1 and P2 such that the delivery flow
rates of the first and second pumps P1 and P2 each coincide with
their target flow rates. Further, since this is not a swing/arm
combined operation, the target flow rate of the third pump P3 is
set to zero, and the electric motor M is not operated.
The arm pilot pressures PL1 and PL2 outputted from the arm
operation device 19 switch-operate the directional control valves
V1 and V4 to the left or right. The bucket pilot pressures PL3 and
PL4 outputted from the bucket operation device 20 switch-operate
the directional control valve V2 to the left or right.
As a result, in accordance with the operation of the arm operation
lever 19b, the hydraulic fluid is supplied to the arm cylinder 8
from the second pump hydraulic line L2, and, in accordance with the
operation of the bucket operation lever 20b, the hydraulic fluid is
supplied to the bucket cylinder 9 from the first pump hydraulic
line L1, thus realizing the arm/bucket combined operation. At this
time, the electric motor M is not operated, so that no hydraulic
fluid is supplied to the arm cylinder 8 from the third hydraulic
pump P3.
(Arm/Bucket/Swing Combined Operation (Light Load))
When the arm operation lever 19b, the bucket operation lever 20b,
and the swing operation lever 21b are simultaneously operated, the
pilot pressures PL1 and PL2, the pilot pressures PL3 and PL4, and
the pilot pressures PL5 and PL6 are respectively outputted from the
pilot valves 19a through 21a in accordance with the operational
direction and operation amount of each lever.
The controller 18 controls the delivery flow rates of the first
through third pumps P1 through P3 based on the control flow of FIG.
3. First, Pow12 is determined from the engine speed, and Pow3 is
determined from the battery charging amount. When the battery
charging amount becomes less than a predetermined value (SOC2 in
FIG. 4B), Pow3 is reduced to zero, and the third pump target flow
rate computed later is reduced to zero, so that, when the battery
charging amount becomes less than the predetermined amount, the
electric motor M driving the third pump P3 is not operated.
The computation of the reference flow rate of each pump of FIG. 5
will be described. Referring to table T1, Qa1 is determined from
the maximum operation pressure PLm1 (which, in this case, is the
bucket operation pilot pressure) of the actuators connected to the
first pump P1. Further, referring to table T2, Qa2 is determined
from the maximum operation pressure PLm2 (which, in this case, is
the maximum value of the arm operation pilot pressure and the swing
operation pilot pressure) of the actuators connected to the second
pump P2. Through the flow rate computation C1, Q12b is determined
from the first and second pump delivery pressures Sv1 and Sv2 and
the first/second pump reference power Pow12, and the minimum value
of Q1a and Q12b is used as the first pump reference flow rate Q1c,
and the minimum value of Q2a and Q12b is used as the second pump
reference flow rate Q2c.
Further, referring to table T3, the reference flow rate Qa3 is
determined from the maximum operation pressure PLm3 (which, in this
case, is the arm operation pilot pressure) of the actuators
connected to the third pump P3. Through the flow rate computation
C2, the reference flow rate Q3b is determined from the third pump
delivery pressures Sv3 and the third pump reference power Pow3, and
the minimum value of the reference flow rates Q3a and Q3b is used
as the third pump reference flow rate Q3c. It is noted here that
assuming that the swing/arm combined operation is performed and
that the arm load pressure is of light load (Pam1 or less in FIG.
6), the third pump target flow rate Q3d is Q3c, and the second pump
target flow rate Q2d is what is obtained by subtracting Q3c from
the second pump reference flow rate Q2c. The first pump target flow
rate is not corrected, and Q1d is Q1c.
Based on the pump target flow rates calculated as described above,
the tilting angle of the first and second pumps P1 and P2 and the
motor speed of the electric motor M driving the third pump P3 are
controlled.
The pilot pressures PL1 and PL2 outputted from the arm operation
device 19 are respectively guided to the left pilot pressure
receiving portions of the directional control valves V1 and V4 and
to the right pilot pressure receiving portions of the directional
control valves V1 and V4, switch-operating the directional control
valves V1 and V4 to the left or right. The pilot pressures PL3 and
PL4 outputted from the bucket operation device 20 are respectively
guided to the left pilot pressure receiving portion and to the
right pilot pressure receiving portion of the directional control
valve V2, switch-operating the directional control valve V2 to the
left or right. The pilot pressures PL5 and PL6 outputted from the
swing operation device 21 are respectively guided to the left pilot
pressure receiving portion and to the right pilot pressure
receiving portion of the directional control valve V3,
switch-operating the directional control valve V3 to the left or
right.
As a result, the hydraulic fluid is supplied from the third pump P3
to the arm cylinder 8 in accordance with the operation of the arm
operation lever 19b, the hydraulic fluid is supplied from the first
pump P1 to the bucket cylinder 9 in accordance with the operation
of the bucket operation lever 20b, the hydraulic fluid is supplied
from the second pump P2 to the swing hydraulic motor 10 in
accordance with the operation of the swing operation lever 21b, and
an arm/bucket/swing combined operation in a light load work is
realized. At this time, the second pump hydraulic line L2
communicates with both the arm cylinder 8 and the swing hydraulic
motor 10 via the directional control valves V1 and V2. However, the
directional control valve V1 is provided on the downstream side in
a tandem connection with respect to the directional control valve
V3, and a restrictor is provided in the parallel hydraulic line L4,
so that the delivered hydraulic fluid from the second pump P2 is
scarcely supplied to the arm cylinder 8. Thus, almost no pressure
loss is generated in the control restrictor dividing the delivered
hydraulic fluid from the second pump P2 to the arm cylinder 8.
(Arm/Bucket/Swing Combined Operation (Heavy Load))
When the arm operation lever 19b, the bucket operation lever 20b,
and the swing operation lever 21b are simultaneously operated, the
pilot pressures PL1 through PL6 are outputted from the pilot valves
19a through 21a in accordance with the operation of each operation
lever.
The controller 18 controls the delivery flow rates of the first
through third pumps P1 through P3 based on the control flow of FIG.
3. It is noted here that when the arm load pressure reaches a
predetermined value or more (Pam2 or more in FIG. 6), the
correction gain G of the third pump is reduced to zero, and the
corrected third pump reference flow rate is reduced to zero. As a
result, the third pump target flow rate is reduced to zero, and the
second pump target flow rate coincides with the second pump
reference flow rate.
The pilot pressures PL1 and PL2 outputted from the arm operation
device 19 are respectively guided to the left pilot pressure
receiving portions of the directional control valves V1 and V4 and
to the right pilot pressure receiving portions of the directional
control valves V1 and V4, switch-operating the directional control
valves V1 and V4 to the left or right side. The pilot pressures PL3
and PL4 outputted from the bucket operation device 20 are
respectively guided to the left pilot pressure receiving portion
and to the right pilot pressure receiving portion of the
directional control valve V2, switch-operating the directional
control valve V2 to the left or right side. The pilot pressures PL5
and PL6 outputted from the swing operation device 21 are
respectively guided to the left pilot pressure receiving portion
and to the right pilot pressure receiving portion of the
directional control valve V3, switch-operating the directional
control valve V3 to the left or right side.
As a result, the delivered hydraulic fluid from the second pump P2
is divided and supplied to the arm cylinder 8 and the swing
hydraulic motor 10 in accordance with the operation of the arm
operation lever 19b and the swing operation lever 21b, and the
delivered hydraulic fluid from the first pump P1 is supplied to the
bucket cylinder 9 in accordance with the operation of the bucket
operation lever 20b, thus realizing the arm/bucket/swing combined
operation in a heavy load work. At this time, the electric motor M
is not operated, so that no hydraulic fluid is supplied from the
third pump P3 to the arm cylinder 8.
In the hydraulic drive system according to the present embodiment,
FIG. 9 is a diagram illustrating the relationship between drive
modes M1 through M8 determined by a combination of the arm load
pressure (light-load/heavy-load), the arm operation
(single/combined), and the arm drive source (second pump P2/third
pump P3), and the energy loss (drag loss, pressure loss, and
electric power loss) generated in each drive mode.
(Drive Modes M1 and M2)
In a light load work using the arm alone, when the arm cylinder 8
is driven by the engine-driven second pump P2 (drive mode M1), the
drag loss accompanying the driving of the third pump P3 and the
electric power loss accompanying the operation of the electric
motor M are not generated. Further, the delivered hydraulic fluid
from the second pump P2 is only supplied to the arm cylinder 8, so
that the pressure loss accompanying the flow division is not
generated. On the other hand, when the arm cylinder 8 is driven by
the electric-motor-driven third pump P3 (drive mode M2), the
pressure loss accompanying the flow division is not generated as in
the drive mode M1. However, the drag loss accompanying the driving
of the third pump P3 and the electric power loss accompanying the
operation of the electric motor M are generated. Thus, in a light
load work in which the arm is used singly, the energy loss is
smaller (the fuel efficiency is better) when the arm cylinder 8 is
driven by the engine-driven second pump P2 (drive mode M5 is
selected).
(Drive Modes M3 and M4)
In a swing/arm combined light load work, when the arm cylinder 8
and the swing hydraulic motor 10 are driven by the engine-driven
second pump P2 (drive mode M3), the drag loss accompanying the
driving of the third pump P3 and the electric power loss
accompanying the operation of the electric motor M are not
generated. However, the second pump P2 communicates with the arm
cylinder 8 and the swing hydraulic motor 10, and a large amount of
hydraulic fluid is divided and supplied from the second pump P2 to
the arm cylinder 8 of low load pressure, so that a large pressure
loss is generated. On the other hand, when the swing hydraulic
motor 10 is driven by the second pump P2, and the arm cylinder 8 is
driven by the third pump P3 (drive mode M4), the drag loss
accompanying the driving of the third pump P3 and the electric
power loss accompanying the operation of the electric motor M are
generated. However, since the arm load pressure is low and the
consumption power of the electric motor M is small, the electric
power loss is small. Further, the delivered hydraulic fluid from
the second pump P2 is only supplied to the swing hydraulic motor
10, so that the pressure loss accompanying the flow division is not
generated. Thus, in a swing/arm combined light load work, the
energy loss is smaller (the fuel efficiency is better) when the arm
cylinder 8 is driven by the electric-motor-driven third pump P3
(drive mode M4 is selected).
(Drive Modes M5 and M6)
In a heavy load work using the arm singly, when the arm cylinder 8
is driven by the engine-driven second pump P2 (drive mode M5), the
drag loss accompanying the driving of the third pump P3 and the
electric power loss accompanying the operation of the electric
motor M are not generated. Further, the delivered hydraulic fluid
from the second pump P2 is only supplied to the arm cylinder 8, so
that the pressure loss accompanying the flow division is not
generated. On the other hand, when the arm cylinder 8 is driven by
the electric-motor-driven third pump P3 (drive mode M6), the drag
loss accompanying the driving of the third pump P3 and the electric
power loss accompanying the operation of the electric motor M are
generated. However, the load pressure in the arm cylinder 8 is low
and the consumption electric power of the electric motor M is
small, so that the electric power loss is small. Thus, in a heavy
load work in which only the arm is used, the energy loss is smaller
(the fuel efficiency is better) when the arm cylinder 8 is driven
by the engine-driven second pump P2 (drive mode M5 is
selected).
(Drive Modes M7 and M8)
In a swing/arm combined heavy load work, when the arm cylinder 8
and the swing hydraulic motor 10 are simultaneously driven by the
engine-driven second pump P2 (drive mode M7), the drag loss
accompanying the driving of the third pump P3 and the electric
power loss accompanying the operation of the electric motor M are
not generated. At this time, the second pump P2 communicates with
the arm cylinder 8 and the swing hydraulic motor 10. However, the
arm load pressure is high and the amount of hydraulic fluid divided
and supplied to the arm cylinder 8 from the second pump P2 is
small, so that no great pressure loss is generated. On the other
hand, when the swing hydraulic motor 10 is driven by the second
pump P2, and the arm cylinder 8 is driven by the third pump P3
(drive mode M8), the delivered hydraulic fluid from the second pump
P2 is only supplied to the swing hydraulic motor 10, so that the
pressure loss accompanying the flow division is not generated.
However, the drag loss accompanying the driving of the third pump
P3 is generated, and due to the driving of the arm cylinder 8 of
high load pressure by the electric-motor-driven third pump P3, the
consumption electric power of the electric motor M increases, and a
large electric power loss is generated. Thus, in a swing/arm
combined heavy load work, the energy loss is smaller (the fuel
efficiency is better) when the arm cylinder 8 is driven by the
engine-driven second pump P2 (drive mode M7 is selected).
In the hydraulic drive system according to the present embodiment,
the controller 18 executes the control flow shown in FIG. 3,
whereby one of the drive modes M1, M4, M5, and M7, which are of
small energy loss (of satisfactory fuel efficiency), is selected in
correspondence with the arm operation, the swing operation, and the
arm load pressure.
--Advantage--
According to the embodiment of the present invention described
above, at the time of the single operation in which only the arm
cylinder 8 of the plurality of actuators 8 and 10 connected to the
second pump hydraulic line L2 is operated, the electric motor M is
not operated, and the arm cylinder 8 is driven by the second pump
P2, whereby it is possible to suppress the generation of the drag
loss accompanying the driving of the third hydraulic pump P3. On
the other hand, at the time of the combined operation in which the
plurality of actuators 8 and 10 including the arm cylinder 8
connected to the second pump hydraulic line L2 are simultaneously
operated, the electric motor M is operated, and the arm cylinder 8
is driven by the third pump P3, whereby it is possible to suppress
the pressure loss which is generated when the delivered hydraulic
fluid from the second pump P2 is divided and supplied to the arm
cylinder 8. In this way, the arm cylinder 8 is selectively driven
by the engine-driven second pump P2 and the electric-motor-driven
third pump P3 in accordance with the arm operation and the swing
operation, and the pressure loss accompanying the flow division and
the drag loss accompanying the driving of the third pump P3 are
suppressed, whereby it is possible to improve the fuel efficiency
of the work machine. The arm cylinder 8, which frequently undergoes
combined operation in light load work and which requires a high
flow rate, is used as the specific actuator that can be selectively
driven by the second pump P2 and the third pump P3, whereby it is
possible to enhance the effect of suppressing the pressure loss and
the drag loss as compared with the case where some other actuator
is used as the specific actuator.
Further, in the embodiment of the present invention described
above, the electric motor M is not operated in a heavy load work
(in which the load pressure of the arm cylinder 8 is Pam2 or more),
and the arm cylinder 8 is driven by the second pump P2, whereby it
is possible to prevent an excessive increase in the electric power
consumption of the electric motor M, and to prevent an increase in
the electric power loss accompanying the operation of the electric
motor M.
Further, in the embodiment of the present invention described
above, the electric motor M is not operated when abnormality is
generated in the electric system related to the driving of the
third pump P3, and the delivered hydraulic fluid from the
engine-driven second pump P2 is divided and supplied to the arm
cylinder 8 and the swing hydraulic motor 10, whereby it is possible
to prevent serious failure related to the electric system, and to
maintain an operability equivalent to that in the prior art.
Further, also in the case where the residual amount of the battery
14 is insufficient, the electric motor M is not operated, and the
delivered hydraulic fluid from the engine-driven second pump P2 is
divided and supplied to the arm cylinder 8 and the swing hydraulic
motor 10, whereby it is possible to maintain an operability
equivalent to that in the prior art.
DESCRIPTION OF REFERENCE CHARACTERS
1: Lower track structure 2: Upper swing structure 2a: Swing frame
3: Front work device 4: Boom 5: Arm 6: Bucket 7: Boom cylinder 8:
Arm cylinder (second actuator/specific actuator) 9: Bucket cylinder
(first actuator) 10: Swing hydraulic motor (second actuator) 11a,
11b: Crawler 12a, 12b: Traveling hydraulic motor 13: Engine 14:
Battery 15: Control valve 17: Pilot hydraulic fluid source 18: Main
controller (control device) 19: Arm operation device 20: Bucket
operation device 21: Swing operation device 19a through 21a: Pilot
valves 19b: Arm operation lever 20b: Bucket operation lever 21b:
Swing operation lever 22: Battery controller (charging rate
detection device) 23: First inverter controller 24: Second inverter
controller 25: Generator motor thermistor 26: Electric motor
thermistor 30: Electric system GM: Generator motor INV1: First
inverter INV2: Second inverter L1: First pump hydraulic line L2:
Second pump hydraulic line L3: Third pump hydraulic line L4:
Parallel hydraulic line L5: Head side hydraulic line L6: Rod side
hydraulic line M: Electric motor M1 through M8: Drive modes P1:
First pump P2: Second pump P3: Third pump PL1 through PL6: Pilot
pressures R1: First pump regulator R2: Second pump regulator S1
through S3: Pump pressure sensors S4, S5: Load pressure sensor
(load pressure detection device) S6 through S11: Pilot pressure
sensors (operation amount detection devices) T1, T2: Conversion
table V1: Directional control valve (second directional control
valve) V2: Directional control valve (first directional control
valve) V3: Directional control valve (second directional control
valve) V4: Directional control valve (third directional control
valve)
* * * * *